As long as it's a 4R75W 4.6/5.4 you are good to go! Also, don't forget to flush out your cooler lines, and if you tow/plow make sure you have an adequate cooling system in place. Worst thing (well maybe not the worst) but people get a new trans, and they do not flush their lines and all that crap that was in their bad one is going right into their new. Also for tow/haul/plow an air to cooler is recommended... image your regular cooler being your appendix, get that sucker out, and ad a nice aftermarket air to oil cooler and you'll be gold.

 

We literally rebuild 5-6 of these a month with 1 builder in the shop (we'd build more but time is not on our side with other transmissions needing attention too)...We do core exchange, meaning they pick up one prebuilt and install giving us theirs. The only issues we ever have is the installer missing the converter and f'n up the pump. If you want to get a rebuild, make sure you go to a reputable builder. We offer a year warranty, but if built right, these transmissions get more than their worth and then some. Some places charge less but they also reuse a lot of crap they shouldn't. A complete rebuild with new bushing, gaskets, seals, direct drum, filter, fwd clutches and steels, intermediate sprag, rev frictions and steels, OD band, servo, sep plate & gasket . . . valve body gone through from us in NJ is $1100 for W and $1200 for E's... we always hear that our price on these units is #cKn great.. but I dunno where you're located.. at least this can help you base it a bit. But the point of my answer, if built correct, it shouldn't be a problem buying another unit and putting it in. As long as it's the same unit

 

YES... there are differences.. check out my pics below with the plugs

 

I hate to inform you that your boss is incorrect. The way to tell if you have a W or E is to look at the left side of the trans. A W trans will only have one senor (an output shaft speed sensor) at the back and an E will have two (a TSS and Output shaft speed sensor).

The picture of the black W connector you posted is used by both the 4R70/75W and the 4R70/75E (2004 to 2008) because they share the same hard internal wire harness. The one you show as E is for the 2009+ 4R70/75E's with the newer soft internal wire harness.

 

The sensors are different.. as you mentioned I was referring to the 04-08 W. The W also has a hole on the bottom of the bell housing and the E does not. Trust me, I've had him explain and show me 1001 times. We build so many of these a month that I had to make those references for W's 04-08 and E's 09-14 to help customers prior to arriving so they can do a core exchange and to verify it is 100% the right one. (This is by a old head builders lingo like how a 46re is a 518...and 41te is a 604 & 47re/48re are 618's)... We have yet to be have one come back wrong. The internet and even Transtar calls W's E's which confuses the haiata outta me. But for all intents and purposes... 04-08 have 2 sensors and so do 09-14. 04-08 W | 09-14 E...

(Edit: I just asked him again about the plug: here's our convo)
Me: The E has a rectangular plug right, and the W a hexagon.?
Him: Right, I call it a W because it has the same plug as the 98-03 but the internet calls it an E...
Me: Ohhhhh, ok, so that's why when you order parts Nick knows what your talking about.
Him: Right, builders call it a W when auto repair shops call it an E


So, as you can see my understanding of it hasn't failed us... and if anyone is Local to NJ. We do have them

 

The 2004-2008 4R70/75E's also had a hole in the bottom of the bellhousing. IIRC, it wasn't until 2009 when they stopped putting the holes in the bottom.

You seem to be stuck in the mindset that all 2004-2008 transmissions are W designated, they are not. Ford starting putting the E transmissions in vehicles in 2004. They are designated as E because they added the extra sensor to transmission (as well as changing some of the internal parts). So remember, W transmissions only have one sensor on the side. E transmissions have two sensors on the side. If you're calling any of the transmissions with two sensors a W, that's incorrect.

As for the connectors (plugs), the 98+ W transmissions and 2004-2008 E transmissions all use the same hexagonal plug. They use the same one because they all use the same hard plastic internal harness. In 2009, Ford went back to a soft internal harness. That's the only reason why it has a different rectangular plug.

I can understand calling it a connector (plug) for a W when talking to your parts guy or around the shop, it's probably easier. The problem is you posted the picture earlier showing that if it has the hexagonal plug it's a W, which isn't entirely correct. That connector is used for both W's and E's and you stating otherwise is going to confuse someone looking for information, as is you saying that all 2004-2008 transmissions are W's.